1. Field of the Invention
The present invention relates to a counter weight to be used for a construction machine or the like.
2. Description of the Related Art
A construction machine such as a hydraulic shovel or the like is generally used for a counter weight. In other words, as shown in FIG. 8, a hydraulic shovel is provided with a lower traveling body 51, and an upper pivoting body 52 to be pivotably fitted in this lower traveling body 51 via a pivoting mechanism; and a counter weight 53 is arranged at a rear part of this upper pivoting body. In addition, an operating machine 54 is connected to the upper pivoting body 52. This operating machine 54 is provided with a boom 55, of which base is swingably coupled with the upper pivoting body 52; an arm 56 that is swingably coupled with a front end of this boom 55; and a bucket 57 that is swingably coupled with a front end of this arm 56.
Then, as this counter weight 53, a chassis made of a copper sheet housing many have-weight objects (for example, see a patent document 1), a framework made of plural blocks covering this framework with an outer surface (for example, see a patent document 2), and further, an object having a lower counter weight having an iron sheet accumulated therein, a middle counter weight having the iron sheet accumulated therein, and a lower counter having the iron sheet accumulated therein (for example, see a patent document 3) are available.
The counter weight described in the above-described patent document 1, as shown in FIG. 9, has a chassis 60 made of a copper sheet and plural heavy-weight objects 61 . . . contained in the chassis 60. In this case, the chassis 60 comprises a bottom plate 60a, an upper plate 60b, a front plate 60c, and a rear plate 60d; and a hollow chamber containing the heavy-weight objects (block) 61 therein is formed, and this hollow chamber is filled up. In addition, with the plural heavy-weight objects 61 . . . accumulated, a bolt member 62 to be inserted through the upper and lower heavy-weight objects 61 is screwed to the bottom plate 60a, and thereby, the counter weight is fixed within this chassis 60.
In addition, in the counter weight described in the patent document 2, as shown in FIG. 10, a plurality of blocks 63 is accumulated vertically to form a framework 64, and the outer surface of this framework 64 is coated with a cover 65. Then, by means of welding or the like, respective blocks 63 are joined, and the framework 64 is joined with the cover 65. In addition, the counter weight described in the patent document 3 is configured by the middle counter weight and the upper counter weight and as same as the above-described patent document 2, the plural blocks are vertically accumulated so as to form the framework, and this framework is coated with the cover. As the block 63 for the counter weight described in the patent document 2, for example, a slab material is used. There is a conventional example using a rejected slab material as the heavy-weight object of the counterweight (for example, see a patent document 4).
[A Patent Document 1]
JP-A-8-199630 (pp. 3–4, FIG. 1)
[A Patent Document 2]
JP-A-2000-302376 (pp. 4–5, FIG. 1)
[A Patent Document 3]
JP-A-2000-63082 (pp. 2–3, FIG. 1, FIG. 2)
[A Patent Document 4]
JP-A-2000-225458 (pp. 4–5, FIG. 7)
By the way, the counter weight of the construction machine is attached to a vehicle frame by fitting a counter weight attaching part of this vehicle frame with a lower face of the counter weight. Therefore, for this fitting, a concavoconvex part is provided at the lower face of the counter weight so as to form a fitting part. Thus, as shown in the above-described FIG. 9, if the bottom plate 60a of the chassis 60 is made of a flat plate, the concavity and convexity are formed in response to this concavoconvex part, so that the counter weight cannot house the heavy-weight object 61 stably. Further, a machine room having an engine or the like housed therein is formed in the upper pivoting body of the construction machine and a rear opening of this machine room is filled up with the counter weight. Thus, it is the often the case that the. concavoconvex part is formed for an engine and a piping to be connected to the engine in the inside of the counter weight (a face corresponding to the machine room) Even in such a case, it is difficult to form the concavoconvex part in the counter weight shown in the above-described FIG. 9. In other words, it is necessary to form respective heavy-weight objects 61 into intricate shapes in accordance with the shape of the chassis 60, and this makes it difficult to manufacture the counter weight and makes the manufacturing cost thereof higher.
In addition, according to the counter weight shown in the above-described FIG. 10, the heavy-weight object of the framework is attached to the vehicle frame. Therefore, it is necessary to make the lower face shape of this the lowest heavy-weight object into the shape in accordance with the counter weight attaching part of this vehicle frame. However, since this heavy-weight object is configured by a slab material, it is necessary to machine this slab material by cutting and it is difficult to cut the slab material into the shape in accordance with the counter weight attaching part with a high precision. In other words, if the heavy-weight object is configured by the slab material as this counter weight shown in FIG. 10, and that described in the above-described patent document 4, the shape of the heavy-weight object (block) becomes intricate, and this results in decreasing of yield of cutting and in making welding of respective heavy-weight objects complicated. Therefore, as same as the above-described counter weight shown in FIG. 9, the manufacturing cost of the counter weight becomes high.
Thus, according to the counter weight described in the patent document 2, it is difficult to form the attaching part to the vehicle frame with high precision, and depending on a degree of alignment to the shape of the counter weight attaching part at the vehicle frame side, it is feared that misalignment and a slope or the like are generated in an external design of the built counter weight and a commercial value thereof is lowered.
In addition, according to the counter weight described in the patent document 3, in the upper counter weight and the middle counterweight, a plurality of iron plates is accumulated, respectively, so that its manufacturing cost is high. Further, this counter weight has the upper and middle counter weights, and this result in complicated manufacture of the counter weight.